Straight edges for drafting boards and the like



Nov. 8, 1966 J. A. TRUHON 3,233,410

STRAIGHT EDGES FOR DRAFTING BOARDS AND THE LIKE Filed Jan. 27. 1965 I ATTORNEY United States Patent 3,283,410 STRAIGHT EDGES FOR DRAFTING BOARDS AND THE LIKE John A. Truhon, 16514 Blackstone, Detroit, Mich. Filed Jan. 27, 1965, Ser. No. 428,415

1 Claim. (Cl. 33-80) This invention relates to straight edges particularly adapted for use on drafting boards or the like; however, they may be employed in other environments.

The primary object of the invention is to provide a light-weight straight edge preferably of extruded aluminum of a combination of aluminum and plastic extrusions comprising an extruded and anodized major straight edge member including a central inverted U-shaped hand grip portion and obtusely extending integral runners, and a cover member closing the central inverted U-shaped hand grip portion providing a longitudinal tunnel through the straight edge to accommodate conventional pulleys and guide cord means employed to guide the straight edge in a parallel path when manually moved transversely of said drawing board, and, interlock means between said major straight edge member and said cover member causing them to act as an integral whole whereby to increase resistance to flexural and torsional stresses on said straight edge during handling and use thereof.

Another object of the invention is to provide a straight edge of the class aforesaid wherein the tunnel thereof which accommodates the pulleys and guide cord means has a readily and conveniently removable and replaceable arch type cover member employed also to reinforce the major straight edge member by interengagement of the abutments of the said arch type cover member therewith when the straight edge is in its assembled useable condition.

A further object of the invention is to provide a straight edge of the aforesaid characteristics which is economical to manufacture, is light in weight, and is resistant to hard usage without breakage or misalignment.

Other objects of the invention will become obvious by reference to the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a top plan view of :a drawing board equipped with a straight edge embodying the invention.

FIG. 2 is an enlarged cross sectional view taken substantially on the line 22 of FIG. 1.

FIG. 3 is an enlarged longitudinal elevational view taken on the line 3-3 of FIG. 1.

FIG. 4 is an exploded cross sectional view of a straight edge construction embodying the invention.

Referring now to the drawings wherein like reference numerals refer to like and corresponding parts throughout the several views, the illustrative embodiment of a straight edge 10 of the invention is shown in FIG. 1 in operative position on a drawing board 11.

The straight edge 10 comprises an extruded and anodized major straight edge member 12 and a cover member 13 which extends the full length of the straight edge member 12 and interlocks therewith to provide in effect a unitary straight edge structure 10. The interlocking of the cover member 13 with the straight edge member 12 is such as will cause them to act as a unitary whole whereby structurally to increase resistance of the straight edge 10 to flexural and torsional stresses during handling 'and use thereof. The interlocking of the said cover member 13 and straight edge member 12 is accomplished in such a manner that the cover member 13 readily may be removed from the straight edge member 12 for access to pulleys 14 and the guide cord 15 within a tunnel 16 formed by said straight edge member 12 and cover member 13 along the full length of the straight edge 10.

The straight edge member 12 is formed with a central i U-shaped hand grip portion having a base and vertically disposed finger or hand grip rails 121 terminating in upper outwardly disposed ribs 122. Extending outwardly and downwardly from said base portion are a pair of obtusely disposed runners 123 formed with a narrow lower shoe 124 which travels on a drawing (not shown) customarily tacked or taped on the drawing'board 11. Thus, the base 120 of the straight edge member 12 is disposed above the runners 123 and shoes 124 to provide a minimum of contact between the straight edge 10 and a drawing removably secured on the drawing board 11. A pair of upwardly and longitudinally disposed anchorage ribs 125 may be provided along each side of the top of the base 120 spaced from the inner walls of the finger or hand grip rails 121 to telescopinglyand frictionally receive the lower portion of the abutment walls 131 of the flat arch of the cover member 13.

The cover member 13 is preferably extruded of a tough relatively rigid plastic in the form of a flat arch 130 with depending abutment walls 131. Obviously, other suit- :able material such as extruded and anodized aluminum may be used for the said cover member 13. The width of the flat arch 130 of the cover member 13 is substan- .tially the same as the distance between the inside of the walls of the finger or hand grip rails 121; however, the depending abutments 131 of'the cover member 13 are formed to slope outwardly and downwardly so that the distance between the outside of the abutment wall 131 at the bottom thereof is slightly wider than the distance between the inside walls of the finger or hand grip rails 121. This permits the cover member 13 to be sprung tightly in place between the inside walls of the finger or hand grip rails 121, the flat arch 130 of the cover member 13 flexing so that surface-to-surface contact is had between the abut-ment walls 131 of the cover member 13 and the inside walls of the finger or hand grip rails 121 of the straight edge member 12 when the said cover member 13 is assembled thereon. This construction insures a substantial unitary effect of the said assembly in resistance to flexural and torsional stresses to which the straight edge 10 may be subjected during handling and when in use.

To assure that the lower portions of the abutment walls 131 of the cover member 13 are disposed and remain disposed tightly adjacent the inside walls of the finger or hand grip r-ails 121 of the straight edge member 12, they are preferably positioned in the longitudinal grooves 125 formed adjacent the inner walls of the finger or hand grip rails 121 by the anchorage ribs 126 of the said straight edge member 12.

A horizontally disposed double grooved pulley 14 is rotatably mounted inwardly of each end of the straight edge member 12 on a vertically disposed bearing shaft 18 suitably fixed to and through the base 120 of the said straight edge member 12 near the ends and laterally central thereof. The said pulleys 14 are completely enclosed within the tunnel 16 of the straight edge, and receive in the grooves thereof the guide cord 15 preferably as later described.

A guide cord anchor 20 is secured to the drafting board 11 at each corner thereof to permit the guide cord 15 for the straight edge 10 to be anchored thereat. The guide cord anchor 20 preferably consists of an inverted U-shaped base 200 having one leg 201 longer than the other. The said long leg 201 is secured by suitable screws 21 to the edge of the drafting board 11. The short leg 202 of the said U-shaped base 200 preferably rests on the top of the drafting board 11 as best shown in FIG. 2. The transverse portion 203 of the said U- shaped base 200 is centrally apertured to accommodate thereon a hollow cylindrical anchorage post 205 shoul- Patented Nov. 8, 1966 i jdered and peened over at its lower end for securement thereto. The upper portion of the anchorage post 205 is suitably shouldered at 2050 to support the guide cord 15 thereon at such a height above the drafting board 11 '1 to admit of the said guide cord 15 entering the tunnel 16 of the straight edge 10 through suitable notches 127 and 132 provided in the finger or hand grip rails 121 of the lthe upper shoulder 2050 thereof. A coin slot headed anchorage screw 206 extends freely through the anchorage post 205 and is threaded into a nut 207 fixed on the lower end of the said anchorage post 205 below the transverse portion 203 of the U-shaped base 200 of the guide cord anchor 20. The tightening of the anchorage screw 206 removably fixes the anchor cord 15 in its strung position on the anchor post 205 of the guide cord anchor between its upper shoulder 2050 and the clamping washer 204.

As best shown in FIGS. 1 and 2, the guide cord 15 is preferably anchored to cord anchor A and extends approximately 90 degrees around the lower groove of the pulley X, extends to and approximately 90 degrees around the upper groove of the pulley Y, to and approximately 90 degrees around anchors C and B and back to the upper groove of pulley X, extends approximately 90 degrees around the lower groove of pulley X, to and approximately 90 degrees around the upper groove of pulley Y from whence it extends to and is anchored -by the cord anchor D. Such stringing of the guide cord 15 substantially eliminates friction on the guide cord 15 Where it crosses itself at a :point central between the pulleys X and Y. To dovetail with the foregoing description of the preferred stringing and anchoring of the guide cord 15 around the pulleys 14 and the guide cord anchors 20, the pulleys 14 in FIG. 1 have been designated X and Y, and the guide cord anchors 20 in FIG. 1 have been designated A, B, C and D. When the guide cord 15 is strung as hereinabove set forth and pulled taut while the straight edge is positioned parallel to the long edges of the drafting board and the cord anchors 20 are tightened, the straight edge 10 will always follow a parallelpath when moved back and forth on the drawing board 11 with the ends thereof reasonably within limits of the sides of the'said drawing board. 7

The ease of placing and removing the cover-member 13 from the straight edge member 12 of the straight edge 10 permits the guide cord to be strung easily and to be readily adjusted when required by any stretching thereof that may occur during use of the said straight edge 10; Also, due to the herein described construction, the fact that the cover member 13 is removable from the straight edge member 12 does not detract from its ability to reinforce the straight edge 10 when assembled thereto against excess torsional stresses which are apt to occur during careless handling thereof,

Although but a single embodiment of the :invention has been disclosed and described herein, it is obvious that many changes may be made in the size, shape, arrangement and detail of the several elements thereof, all within the scope of the appended claim.

I claim:

A straight edge for drafting boards useable .with conventional guide cord means anchored at the corners of the drafting board and extending along said straight edge and in engagement with pulley means located adjacent each end thereof providing parallel movement of said straight edge on said drafting board comprising an extruded and anodized aluminum U-shaped main straight edge element including a base and a pair of upwardly disposed hand grip elements extending the sides of said base, the base of said straight edge element including downwardly and outwardly disposed runnerstherealong extending from said base and terminating in narrow lower continuous shoes, a for-med arched cover member consisting of a flat arch and downwardly and slightly outwardly disposed.

abutments sprung into. releasable frictional engagement with the inner surface of said hand grip :rails forming ,a tunnel along the top of said straight edge, a pair of vertically disposed ribs along the top of said base of said straight edge element spaced laterally References Cited by the Examiner UNITED STATES PATENTS 866,479 9/ 1907 Kiesel 52-312, 2,509,559 5/1950 Cardinell 33107 2,804,691 9/1957 Justis 33-80 3,106,783 10/1963 "Justis 33-80 3,117,691 1/1964 Williams 320-60 FOREIGN PATENTS 1,081,055 6/ 1954 France. 1,166,886 6/ 1958 France.

LEONARD FORMAN, Primary Examiner.

ISAAC LISANN, Examiner.

HARRY N. HAROIAN, Assistant Examiner, 

